I've done some checking and it looks like compatability is not the issue
When the program was re installed it either didn't install the font "roots" to where Windows XP expects to find it or it hasn't installed it at all.
http://www.rootsusers.org/FAQs/machnew.htm has some help on installing and moving to a new machine including the names of files that may need to be copied over.
1. Check the folder "fonts" within the Windows main folder on C Drive
2. or try using the search facility from the control panel to search for a file called or contaning "Roots"
If the file is in the fonts folder you can try reinstalling the program making sure you have administrator rights (ie the machine authorises you to install programs) or if the font is in another place go to the fonts folder in Windows click on file on the menu bar and select install new font ...... it should ask for a source and you point it to where the roots font is .
If the roots font is not on the machine try checking your installation disks to see if the font is there and try the installation from within the fonts folder
If the font is not there either, then the last solution is to try to get the program to change its default fonts ...... this instruction may be contained within the programs help files.
Sorry I can't help any further